Re: *PING* [PATCH] PR fortran/69419 - ICE: tree check: expected array_type, have real_type in gfc_conv_array_initializer, at fortran/trans-array.c:5618

[Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>]

On Wed, 3 Nov 2021 21:00:41 +0100
Harald Anlauf via Fortran <fortran@gcc.gnu.org> wrote:

> *PING*
> 
> Am 27.10.21 um 21:09 schrieb Harald Anlauf via Fortran:
> > Dear Fortranners,
> > 
> > when debugging the testcase, I noticed that a coarray declaration in
> > a COMMON statement wrongly set the dimension attribute instead of the
> > codimension.  As a consequence, subsequent checks that catch this
> > invalid situation would not trigger.
> > 
> > I see two possible solutions:
> > 
> > - in gfc_match_common, replace
> > 
> > 	  /* Deal with an optional array specification after the
> > 	     symbol name.  */
> > 	  m = gfc_match_array_spec (&as, true, true);

If coarrays are generally forbidden in commons then..
> > 
> >    by
> > 
> >    m = gfc_match_array_spec (&as, true, false);

.. this sounds right to me.

> > 
> >    which in turn would lead to a syntax error.  Interestingly, the Intel
> >    compiler also takes this route and gives a syntax error.
> > 
> > - check the resulting as->corank and emit an error as in the attached
> >    patch.

If we want to be more helpful than a mere syntax error (and we
should be) then yes.
Otherwise we'd have to explicitly
@@ -5275,9 +5275,19 @@ gfc_match_common (void)
 
 	  /* Deal with an optional array specification after the
 	     symbol name.  */
-	  m = gfc_match_array_spec (&as, true, true);
+	  m = gfc_match_array_spec (&as, true, false);
 	  if (m == MATCH_ERROR)
 	    goto cleanup;
+	  if (m == MATCH_NO)
+	    {
+	      /* See if it is a coarray and diagnose it nicely.  */
+	      if (gfc_match_array_spec (&as, false, true) == MATCH_YES)
+		{
+		  gfc_error ("Symbol %qs in COMMON at %C cannot be a "
+			     "coarray", sym->name);
+		  goto cleanup;
+		}
+	    }

where your patch works equally well and is more concise.
Maybe you want to add a test for the double-colon variant too?
   common /c2/ y[:] ! { dg-error "cannot be a coarray" }

A type with a coarray seems to require to be allocatable so is
rejected (properly, but not mentioning the coarray) with
Error: Derived type variable ‘comm_ty1’ in COMMON at (1) has an ultimate component that is allocatable

When reading gfc_match_array_spec i thought that it might have been cleaner
to split the coarray handling out to a separate gfc_match_coarray_spec but
that's what we have.
> > 
> > The attached patch regtests fine on x86_64-pc-linux-gnu.  OK for mainline?

LGTM but i cannot approve it.
Thanks for the patch!